Question

The incredible length of biological polymers (sometimes tens of thousands of monomers) often results in the formation of a tertiary, 3-D structure. An example of this is in globular proteins. Which of these is NOT a force of attraction which usually acts between the different sections of the polypeptide chain of a globular protein?

	1.	Van der Waals' forces
	2.	Hydrogen bonds
	3.	ionic bonds
	4.	Metallic bonds

Answer 1

Answer: Metallic bonds

Explanation:

The two main tertiary structures of a protein are globular and fibrous. Whilst globular proteins are almost spherical in shape and are soluble, fibrous proteins are rope - like strands which are insoluble. Haemoglobin and enzymes are examples of globular proteins. Collagen and keratin are examples of fibrous proteins.

As well as the incorrect answer options(ionic bonds, vander wall's forces.and hydrogen bonds) the di-sulphide bridge (a type of covalent bond) is the forth interaction which can occur between different sections of the polypeptide chain in the tertiary structure of a protein.

Whist ionic bonds and the di-sulphide bridge are classed as intramolecular bonds, the hydrogen bond is classed as an intermolecular bond. The hydrogen bond is both the strongest intermolecular force and one of the most commonly occuring forces of attraction in biologival molecules.